This invention is directed to an insulin delivery system which includes a reservoir, a pump and a control system which delivers insulin at a constant rate in accordance with the basal metabolic need, and in preprandial doses so that insulin is delivered to the body in accordance with bodily need.
The preferred embodiment of this invention is in the delivery of insulin, and the invention is described as an insulin delivery system throughout this specification. However, it is clear that it is useful for the delivery of other medications to the body. For example, Heparin can be usefully delivered by this system. Furthermore, chemotherapy medication can be administered and controlled by the delivery system of this invention. Thus, any medication which should be delivered to the patient throughout the day can be properly administered by this delivery system.
The pump, with or without the disclosed reservoir could be used to inject a radio-opaque medium for arteriography, which is a procedure where the physicians inject a dye in unision with the heartbeats so the progress of the dye can be followed on X-ray. The present pump is such that it can deliver a pulse as a reaction to an outside signal. Thus, an EKG signal can trigger the pump to deliver the dye into the vascular system each time the heart beats. The physicians can use this to detect where the coronary arteries are restricted or plugged.
When delivering insulin, as in the preferred embodiment of the delivery system of this invention, should an implanted continuous glucose sensor become successful and reliable, the output of the sensor can be used to trigger the pump in the delivery system of this invention. The pump is designed so that it can proportionately dispense insulin or other medication in accordance with the pump and drive signal, and this signal can be based on a measured or sensed bodily need.
Physicians have found that when a medication is delivered to the body of the patient in very small doses regularly delivered around the clock, the medical effect is better than if the medication is injected in relatively large, discrete boluses. As a result, a number of devices have been designed which are intended to administer medication at a constant rate. One such prior art device is a syringe pump. A screw feed advances the syringe plunger and thus controls the rate of infusion. This structure requires a substantial amount of power to drive the plunger, and thus the drive motor and the battery are bulky and difficult to conveniently carry on the person. The presently leading screw fit syringe plunger type of mechanism is AUTO-SYRINGE. The structure is large and weighty, and the controls are awkward to manage because they require several calculations and corrections to arrive at the flow rate adjustment. Furthermore, the adjustments are made in discrete steps, allowing little resolution or fineness in control. Additionally, the syringe is exposed and thus can be damaged while the patient wears the syringe. Another commercially available device which employs the same syringe principle is the Mill-Hill Pump which has been developed in England.
A third commercially available device represents a different design approach and is made by Siemens in Germany. The Siemens medication dispenser uses a pump which is a roller pump to propel the medication in the tube. This has as a major disadvantage that, whenever the roller leaves the tubing (as it is supported in its circular arcuate track), the tubing expands and thus the delivery of the medication is slowed down, is stopped or may even be drawn backwards. The roller pump always has a cyclic output. Thus, when such a pump is stepped, the output is not necessarily repeatable. For this reason, the roller pump is not suitable for a precise metering application such as insulin injection. Furthermore, such a roller pump requires a substantial amount of power and thus requires a large battery or frequent battery changes. These pumps are "progressive, non-valved" pumps whereas the invention described herein is a "repeating, valved" pump.
These pumps are "progressive, non-valved" pumps whereas the invention described herein is a "repeating, valved" pump.
Thus, there is need for an insulin delivery system which includes a pump that accurately delivers small increments of liquid medication. Such a pump requires a small chamber because of the small volume pumped to each stroke, and requires properly operating valves which are easily actuated and which prevent reverse flow.